Questions tagged [mathematics]
The abstract study of topics encompassing quantity, structure, space, change, and other properties
112
questions
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Projection: Mollweide to Equirectangular
I am trying to reproduce in Python a coordinate transformation of a map from Mollweide coordinates (see Figure A) to Equirectangular coordinates (see Figure B) that I saw done in Mathematica in the ...
- 483
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0
answers
23
views
Finding Maximal lines from multiple parallel lines
I have a lot of parallel lines in a list, and I am looking for a way to get the maximal lines that include individual lines. For example, let's say I have 10 lines.
l1 = LineString(((0, 0), (8, 8)))
...
- 101
0
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0
answers
19
views
Storing movement vectors in DB
I'm not sure if this question is applicable to here or the stats exchange. Maybe some GIS folk have taken a good look at GIS stats?
I've got a postgres+postgis+timescaledb database that has billions ...
- 1,211
0
votes
0
answers
30
views
Difference between two Google Earth Engine functions
Do you know what is the difference between
ee.Clusterer.wekaKMeans
and
ee.Clusterer.wekaCascadeKMeans?
0
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0
answers
35
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Calculate a centered Midpoint from a set of Lat and Longs in a given region
I am writing an Android app that will display placemarkers in regions you have visited over the world. In order to find where to place these placemarkers I am querying a Gadm36 (world) database for ...
1
vote
0
answers
45
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In Tile coordinates, how to get one zoom-level deeper but span the same area?
For an arbitrary tile region defined by (z1, x1, y1), how can we increase z1 to z1 + 1 but span the exact area defined by (z1, x1, y1)?
For example, consider t1=(2,2,1). If we want zoom=3 for the same ...
4
votes
1
answer
73
views
Wring mathematical formula for Sentinel-1 in Google Earth Engine
I am trying to find permittivity using Sentinel-1 using following expression
It is inverse of Modified Dubois model for soil moisture.
I am new to GEE so I tried to break the expression in to small ...
- 43
0
votes
1
answer
146
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How to convert EPSG:28992 to EPSG:4326?
I have a list of coordinates which I need to convert to longitude and latitude in the following way:
What are the math transformations and formulas used to achieve this?
0
votes
0
answers
75
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Clockwise sorting segments of a polygons
My polygons are divised into an array of lines features. Each segments have only 2 coordinates. I would like to sort those segments clockwise starting from the top-right (north-east) like in the image ...
- 3,424
2
votes
1
answer
57
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Considering distance in network analysis (Gephi)
I have created a set of nodes (archaeological sites) and ties (connected via certain geographical distances), exported from QGIS. I now have an edge list with weights (distances). Gephi, however, sees ...
- 77
0
votes
0
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81
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Band ratio with Euler's number in Google Earth Engine
I've band ratio with exponential equation and Euler's number
band_ratio = (0,0039e)^(2,4952*(B2/B4))
Can anyone write it in Google Earth Engine format?
Or just input the Euler's number?
- 95
1
vote
1
answer
262
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Subtracting image value from corresponding month from image collection in Google Earth Engine
I have extracted sea surface temperature(SST) images from Google Earth Engine for a specific time period and region
var start = ee.Date(2012-01-01);
var end = ee.Date(start).advance(1,'month');
...
- 483
1
vote
1
answer
95
views
An application for measuring river length?
I'm aware of the coastline paradox and its application to rivers in that the measured length of a river depends on the resolution of the measurement.
Is there an application that calculates the centre ...
- 21
3
votes
0
answers
52
views
Dividing polygon into tiny polygons of particular size
I would like to divide/cut an irregular polygon into tiny polygons of a particular size(1.6m x 1m) in such a way that most of the irregular polygon area has to be utilized (an OPTIMIZATION MODEL)
The ...
0
votes
3
answers
328
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How to determine left and right side of crossing lines? [closed]
Given two lines of which we know the starting XY points and intersecting point, I need to find which line is left and which line is right. The lines are always crossing and can be turned in any ...
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1
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0
answers
109
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Determine if a great circle is on the left or right from a point defined by latitude, longitude and bearing
Given
A point coordinate on the map specified by latitude and longitude. Shown as "C" on pictures below.
Direction where this point is moving, specified by bearing in degrees (0-359), where ...
- 119
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0
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24
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How can you completely cover the surface of a raster with circles where the radius of the circle is the raster value at its centroid?
This is more of an algorithmic/math problem, but I was wondering if someone could point me in the right direction. There's the common problem of covering a surface with circles of equal sizes, but ...
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6
votes
1
answer
306
views
Math formula to calculate GPS location for weighted GPS data points
I'm working to improve the location and accuracy of a map / data-point driven application.
I have a collection of locations of interest. Each location of interest has a collection of data points that ...
- 161
1
vote
1
answer
64
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Time-Based Multilateration
I'm not entirely certain, but I think this forum is most appropriate for this question.
I know the location of three observers. A nearby source, who's location is unknown emits a beam of radiation at ...
- 13
1
vote
1
answer
122
views
Finding line equation (on Earth) using two GPS coordinates
Assuming I have two GPS coordinates, how can I find the equation of Earth horizontal line that passes between them?
I tried searching for a method of finding a line on a sphere that passes through two ...
- 121
2
votes
1
answer
166
views
Converting to geodetic latitude, longitude
I’m writing a program to determine a vector between two points on earth by taking the difference of the ECEF vectors for each point. I’m using this algorithm:
https://www.mathworks.com/help/aeroblks/...
3
votes
1
answer
356
views
ECEF coordinates to geodetic coordinates: Where is error in calculation?
I know, there are several questions to this topic, but I am just searching for the error in my own equations. I have no deeper geodetic background, but I am trying to understand these formulas instead ...
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1
vote
1
answer
381
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High resolution x,y dataset for Mollweide projection convert to latitude and longitude coordinates
I have a 2D array that's 144000 x 64000 that has some values that are irrelevant to the question. Let's say the array can be used like an X, Y coordinate system. I somehow need to get the Latitude and ...
- 131
1
vote
1
answer
140
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How to transform camera calibration parameters to other coordinate system?
I have all camera calibration parameters (X0, Y0, focal length, R0, P0, P1, K0, K1, coarse rotation, rotation, translation) and position of the image in WGS84 (XYZ in meters) and other parameters like ...
- 121
3
votes
1
answer
61
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Seeking documentation about non-iterative UTM to Lat-Long projection formulas
In
Hager, John W., James F. Behensky, and Brad W. Drew. "The universal grids: Universal transverse mercator (utm) and universal polar stereographic (ups)." DMA technical manual 8358 (1989).
I ...
- 237
2
votes
0
answers
346
views
Calculating Center (GPS Point) and Radius (km) of n GPS points
I'm new to GPS and position mapping but i have a background in programing and some of the math related to it.
I've been tasked with writing a small golang program that takes n GPS points (DMS) and ...
- 121
1
vote
0
answers
42
views
Converting latitude/longitude into a slab number (or item number) and vice versa?
Purpose: To compress the data transmission for the longitude and the latitude. Initially these datas are in the form DD.MM.mmmm: degrees, minutes, ten thousandths of a minute. Latitude stands under 28 ...
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4
votes
1
answer
300
views
Calculate weighted azimuth/bearing of a line
Given the line
LINESTRING(-9.086532643219698 -7.939337106873815,-1.396102955719698 -0.9775148048290135,-0.780868580719698 -0.7138718839794582,-0.077743580719698 -0.6699297767574899,0.581436106780302 ...
1
vote
0
answers
44
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How is the Point on surface tool calculated in QGIS [duplicate]
I am interested to know how the Point on surface tool works in QGIS 3. I am choosing to use this rather than the Centroids tool which works of the "center of mass" methodology because this creates a ...
- 2,728
1
vote
0
answers
167
views
Applying a two step floating catchment with boundary limitations
The literature states that gravity models and the two step floating catchment area (which in itself is a version of the gravity model) method for analysing the accessibility of healthcare services by ...
- 2,728
3
votes
1
answer
144
views
How to run a Epanechnikov (parabolic) decay in QGIS 3.6 field calculator
Does anyone know how you would implement a Epanechnikov (parabolic) decay to a field in QGIS field calculator. I am trying to apply varying distance decay functions in order to assess the best ...
- 2,728
2
votes
0
answers
327
views
calculating HRMS using NMEA sentences including GPGGA , GPGSV, GLGSV, QZGSV,QZGSA, GPGSA?
I have NMEA sentences including GPGGA , GPGSV, GLGSV, QZGSV,QZGSA, GPGSA and GNGSA. my goal is to achieve HRMS accuracy meter. produced android devices for special intent gives GP/GN GST nmea message ...
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3
votes
1
answer
497
views
Procedure of transforming coordinates?
I'm trying to understand the math behind this transformation. I should note that I've been able to perform the transformation using GeoPandas, but I'd like to understand what is going on under the ...
- 133
2
votes
0
answers
66
views
How to compare centrality of points in different shaped and sized polygons
Suppose I have several polygons of varying shape and size, each containing a single point. I want to compare the centrality of each point, and determine which point is more central to its polygon. I'm ...
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1
vote
2
answers
3k
views
Calculate angle between nodes or point in line in QGIS
I want to check the digitization of line in correct direction, so for that I need to know the angle of each node in line. Is that possible in QGIS?
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6
votes
2
answers
15k
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How to add meters to EPSG:4326 coordinates? [duplicate]
I've some lat/long in EPSG:4326 coordinate system like Eiffel Tower position : ["lat" : 48.858274,"lon" : 2.2944]
For automated tests I would like to get, for every points of my dataset, the x and y ...
- 225
1
vote
0
answers
255
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GRASS GIS: Getting know about stream power index (SPI) computation by r.watershed function
I need to know exact way how stream power index (SPI) is computed by module r.watershed. On the help page is that SPI is α * tan(β), where:
α is cumulative upslope area draining through a point per ...
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2
votes
1
answer
118
views
Postgresql - problem updating row with complex calculation
A calculation for the replacement value of a tree exists:
Variables:
index_price for species;
circumference of tree;
condition measures: vitality, root_injuries, stem_injuries,
crown_injuries
(A ...
- 585
1
vote
1
answer
208
views
What's the math behind moving from a starting point in the direction of another one?
I am working with decimal-degree coordinates for a software and lack geographic background.
I want to convert the coordinates to a grid to calculate distances and then move around using standard ...
- 111
0
votes
1
answer
101
views
Kriging: Large standard error very close to known value points
I am attempting to create surfaces of strata via Kriging in Arc GIS from borehole data. In addition to the predicted surface I also want surfaces showing 95% confidence above and below the predicted ...
1
vote
1
answer
454
views
Formula for transforming from EPSG:4326 to EPSG:3003 or EPSG:3004
This system is used in Italy.
I came across this:
It says that lambda zero is 9° if it's to epsg:3003 otherwise if it's to epsg:3004 it's 15°
I came up with this Java code, but the result is wrong:
...
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2
votes
3
answers
8k
views
Converting from ECEF to geodetic coordinates
I am trying to convert an ECEF coordinate to a geodetic coordinate using this procedure, but I don't fully understand the process. It is prefaced by stating the geodetic parameters {a,b,e,e'} are ...
- 39
1
vote
2
answers
446
views
Calculate turn required to follow a line of latitude
Lines of latitude are not geodesic except at the equator. So to follow perfect eastern course in the northern hemisphere in a vehicle a left turn is constantly required. We can express a turn as the ...
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3
votes
0
answers
631
views
Calculate lat/long as percentage distance between two points (MSSQL)
I've loaded the US road shapes into MSSQL. I've determined the query to locate the segment of road for a specific address. The segment contains a "linestring" from a series of points.
I'm trying to ...
8
votes
2
answers
1k
views
Estimating resolution of vector data?
I got an old vector dataset with polygons covering a continent. The data was first published on paper at scale 1:5 000 000 and was later digitalized. I don't have the original data and no information ...
- 368
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vote
1
answer
5k
views
Translating latitude and longitude into "polar coordinates" around a point
Times Square in New York City has the coordinates (as per Google Maps):
40.7589, -73.9851
The Barrymore Theater has the coordinates (again, as per Google maps):
40.7601, -73.9862
Given that ...
- 125
2
votes
0
answers
2k
views
Finding the Point of Intersection Between Two Line Segments and Level of Error
I am working on calculating the intersection of two lines. Each line segment is represented as two geographic coordinate pairs. Additionally, each line segment is less than 1km in distance.
My ...
2
votes
1
answer
345
views
Creating local coordinate system from orthorectified image from drone
My plan is to use a drone and pix4d to map an area and produce a top down image. I have some position data that is in its own reference frame / Coordinate system.
My question is what suggestions or ...
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4
votes
2
answers
2k
views
How can I calculate the coordinates of a point on the intersection of two parallel lines with a bisecting line with pyQGIS? [closed]
I am building some sort of homemade pyQGIS-Buffer-tool as the existing flat-end-buffer-tools are not working for me ( see v.distance.buffer does not create proper buffers with flat endcaps)
Therefore ...
- 1,419
2
votes
1
answer
79
views
Determine on what side of a line my current position is at, no matter orientation
I know that this question has been up before, but I'll give it a shot since it's not exactly the same question.
Imagine a straight line consisting of a start point and an end point.
The orientation ...
- 137